Polygon highlighting
I don't think there is any way of totally disabling it in blender, but you can get pretty close by changing the theme preferences.

First go to Edit



Then select Preferences



And then in the new window go to Themes -> 3D view -> Face Selected.

Lastly, click the color and turn the lowest value (A or Alpha) to 0 and click at the bottom right of the window "Save Preferences".



Then you should be set.